Preparation, Structure And Antibacterial Activity Of Modified Montmorillonites With Quaternary Phosphonium Cations

In this paper,modified montmorillonites have been prepared by intercalating quaternary phosphonium cations into sodium montmorillonite(Na-MMT) through an ion-exchange method,and the preparing technology,structure and antibacterial activity were studied.Firstly,the preparation process and conditions of the ion-exchanged reaction were optimized.The obtained suitable conditions were as follows:reaction temperature 60℃,reaction time 4h,pH 7,Mol ratio of QPC(quaternary phosphonium cations) to CEC(cations' exchanged counts) of Na-MMT 1.5:1.0.Secondly,the structure of modified montmorillonites was characterized by fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TG),and X-ray diffraction(XRD) and scanning electron microscopy(SEM).Also the zeta potential,specific surface area and desorption content in water of modified montmorillonites were determined.Modified montmorillonites exhibit excellent thermal stability with the onset temperature of decomposition of higher than 210℃, and the basal spacing of modified montmorillonites is enlarged with the increase of quaternary phosphonium cation content and alkyl chain.FT-IR analysis confirmed that the quaternary phosphonium cations were already inserted into the interlayers of montmorillonites.Na/MMT displays flake shape with the particles adhered and interwinded each other,while the modified montmorillonites are formed of irregular shape.The zeta potential increases and the specific surface area decreases with the increase of the quaternary phosphonium cation content in modified montmorillonites. After soaking in distilled water for 60 hours at 40℃,the desorption contents of quaternary phosphonium cations in decyltributyl quaternary phosphonium cation modified montmorillonites(DTBP-MMT),dodecyltributyl quaternary phosphonium cation modified montmorillonites(DDTBP-MMT),tetradecyltributyl quaternary phosphonium cation modified montmorillonites(TDTBP-MMT) and hexadecyltributyl quaternary phosphonium cation modified montmorillonites (HDTBP-MMT) were only 3.5 wt%,2.4 wt%,1.9 wt%and 1.6%,respectively,but the desorption contents of quaternary phosphonium cations increased when soaking in 0.9 wt%saline water.Finally,the antibacterial activity of modified montmorillonites containing tributyl quaternary phosphonium cations of different contents and chain length has been tested,and the antibacterial activity of modified montmorillonites soaking in the water were studied.HDTBP-MMT shows the best antibacterial activity.For the modified montmorillonites with the same quaternary phosphonium cations,the antibacterial activity improves with the increase of the quaternary phosphonium cation content.The modified montmorillonites containing 22.17 wt%of dodecyltributyl quaternary phosphonium cation,possesses the minimal inhibitory concentration(MIC) against Escherichia coli and Staphylococci aureus of 150 mg.l^-1 and 50 mg.l^-1,respectively.After soaking in distilled water for 60 hours at 40℃,the antibacterial activity did not decreased obviously.